Optical isomerism

• What is optical isomerism?

  • A form of stereoisomerism
  • Same structural formula
  • Different arrangement of atoms in space
• What do optical isomers have in common?

  They are mirror images of each other.
• What is a chiral carbon?

  A carbon atom with four different groups attached to it.
• What are enantiomers?


  They are non-superimposable mirror images of each other.
• Why are hands used as an analogy for optical isomers?

  Because they are mirror images and non-superimposable.
• How can you identify a chiral center in a molecule?

  By finding a carbon atom with four different groups surrounding it.
• What is the process for drawing a chiral center in 3D?

  1. Identify the chiral carbon.
  2. Draw the tetrahedral shape.
  3. Use wedges and dashed lines to represent 3D orientation.
• What is the significance of a mirror line in optical isomerism?

  It shows the relationship between two enantiomers.
• What is plane polarized light?

  Light that oscillates in only one direction after passing through a Polaroid filter.
• What happens to plane polarized light when it passes through an optically active compound?

  It rotates either clockwise or anti-clockwise.
• How do enantiomers differ in their effect on plane polarized light?

  One enantiomer rotates it clockwise and the other anti-clockwise.
• What is a racemic mixture?

  An equal mixture of both enantiomers.
• Why do racemic mixtures not rotate plane polarized light?

  Because the rotations of the enantiomers cancel each other out.
• What should you be cautious about when interpreting the results of plane polarized light experiments?

  A lack of rotation does not necessarily mean there are no chiral centers present.
• What is formed when there is an equal amount of each enantiomer in a mixture?

  Racemic mixture
• Why do racemic mixtures not rotate plane polarized light?

  Because the equal amounts of enantiomers rotate light in opposite directions, canceling each other out
• What should you be cautious about when a sample does not rotate plane polarized light?

  It does not necessarily mean that there are no optically active compounds present
• How can a racemic mixture of a chiral product be formed?

  By reacting two non-chiral substances together
• What happens when an alkene reacts with a halogen like bromine?

  It can form a chiral compound if the resulting carbon has four different groups attached
• What is the significance of the thalidomide case in drug development?


  One enantiomer was effective for morning sickness while the other caused severe deformities
• Why is it important to consider the effects of both enantiomers in pharmaceuticals?

  Because one enantiomer may have therapeutic effects while the other may cause harmful side effects
• What type of reaction can lead to the formation of racemic products involving carbonyl groups?

  Nucleophilic attack on unsymmetrical ketones or aldehydes
• What is the role of the cyanide ion in the reaction with aldehydes?

  The cyanide ion acts as a nucleophile attacking the carbonyl carbon
• How does the planar nature of the carbonyl group affect the formation of enantiomers?

  It allows the nucleophile to attack from either above or below, leading to two different enantiomers
• What does it mean for a reaction to produce a racemic mixture?

  It means that both enantiomers are produced in equal amounts
• What is the significance of the mirror images of enantiomers?

  They represent two different configurations of a chiral center
• Why is drug development a lengthy process?

  It involves extensive testing and trials to ensure safety and efficacy
• What factors influence the cost of drug production?

  Cost-benefit analysis, production methods, and market demand
• What are the key terms related to optical isomerism that students should know for exams?

  • Racemic mixture
  • Enantiomers
  • Chiral center
  • Nucleophile
  • Carbonyl group
  • Optical activity
• What are the implications of having both enantiomers in a pharmaceutical drug?

  • One enantiomer may be therapeutic
  • The other may cause side effects
  • Importance of separating enantiomers
  • Cost considerations in drug production
• What are the steps involved in the formation of a racemic mixture from a reaction?

  1. React two non-chiral substances
  2. Form a chiral center during the reaction
  3. Nucleophile attacks from either side
  4. Produce equal amounts of both enantiomers